Premium
Biosynthetic routing of pulmonary surfactant proteins in alveolar type II cells
Author(s) -
Voorhout W. F.,
Weaver T. E.,
Haagsman H. P.,
Geuze H. J.,
Van Golde L. M. G.
Publication year - 1993
Publication title -
microscopy research and technique
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.536
H-Index - 118
eISSN - 1097-0029
pISSN - 1059-910X
DOI - 10.1002/jemt.1070260504
Subject(s) - golgi apparatus , endoplasmic reticulum , pulmonary surfactant , microbiology and biotechnology , immunoelectron microscopy , vesicle , secretory pathway , copi , chemistry , budding , biology , biochemistry , antibody , membrane , immunology
Surfactant proteins A, B, and C (SP‐A, SP‐B, and SP‐C) are synthesized in alveolar type II cells. SP‐B and SP‐C are both synthesized as large precursor molecules that are proteolytically processed to their mature sizes. In a previous immunoelectron microscopic study, we showed that precursor SP‐B is processed to its mature size in multivesicular bodies. In the present study, using a specific antibody aginst precursor SP‐C, we demonstrate that precursor SP‐C is present in the same intracellular compartments of the biosynthetic pathway, i.e., endoplasmic reticulum, Golgi complex, and multivesicular bodies, as precursor SP‐B. Since mature SP‐C is known to be present in multilamellar bodies, this suggests a biosynthetic routing and site of processing of this protein similar to those of SP‐B. Double‐labeling experiments using antibodies against SP‐A, precursor SP‐B, precursor SP‐C, and an antibody against HA I, an adaptor protein involved in the budding of transport vesicles from the Golgi complex, showed that the different surfactant proteins traverse and exit the Golgi complex via the same route. The surfactant proteins do not exit the Golgi complex via HA I‐positive coated buds or vesicles. These data are in accordance with the concept that SP‐A, SP‐B, and SP‐C are transported together through the same biosynthetic pathway via multivesicular bodies to multilamellar bodies. © 1993 Wiley‐Liss, Inc.